In a ruling on Tuesday, the judge who refused to dismiss the case earlier this month denied Cosby's appeal against that decision.

The 78-year-old TV star is accused of drugging and violating an ex-Temple University employee at his Philadelphia home in 2004 and could get 10 years in prison if convicted.

The defence insists Cosby had a promise from a previous district attorney that he would never be charged over the 2004 encounter.

Montgomery County Judge Steven O'Neill, though, found the evidence of such an agreement lacking after hearing from the ex-prosecutor and others at a two-day hearing.

He said the issue does not warrant an immediate appeal that would delay the scheduled March 8 preliminary hearing.

"An immediate appeal from these orders would not materially advance the ultimate termination of the matter," the judge wrote in a brief order.

A spokesman for Cosby's lawyers said it was unclear if they would appeal to the state Superior Court.

Cosby's lawyers have argued the charges stem from a political feud between former district attorney Bruce Castor, who had declined to arrest Cosby a decade ago, and Kevin Steele, who invoked the case as he campaigned against Castor last autumn.

Mr Steele won the race for district attorney and filed charges against Cosby in December, days before the deadline expired.

Dozens of women in recent years have come forward and accused Cosby of sexual impropriety spanning decades.

Cosby, who played Dr Cliff Huxtable on The Cosby Show from 1984 to 1992 and has been married for decades, has denied the women's accusations. The statute of limitations has expired in most of the cases against him.

Cosby, whose legal residence is in western Massachusetts, remains free on 1 million dollar (£700,000) bail.